284 PALAEONTOLOGY OF ILLINOIS. 



POTERIOCEINUS suBRAMULosus, Worthen. 



PI. XX VII, Fig. C. 



Poteriocrinns subramulosus, WOKTHEN, Feb. 1882. 



Bulletin No. 1, of the Illinois State Museum of Natural History, p. 14. 



Body turbinate or obconical, higher than wide to the top of the 

 radial series, and composed of very thin, smooth plates. Basals 

 truncate below, about as high as wide, and forming by themselves 

 a small patagonal cup a little more than half as high as wide. 



Subradials about twice as large as the basals, four of them hexag- 

 onal, and two on the posterior side larger than the others and hep- 

 tagonal. Only two of the rays are preserved in the specimen before 

 me, and in one of these, the right posterior one, the radial plate 

 appears to be quadrangular, and rests directly upon the upper mar- 

 gin of the large posterior subradial below. In the left antero-lateral 

 ray the radial is pentangular, its lower angle fitting in between two 

 of the subradials, as is usually the case in this genus. 



Brachials two, the first quadrangular, and the second pentangular, 

 both wider than long, and the last supporting on its sloping sides 

 the first divisions of the rays. The arms in the right posterior ray 

 divide again two or three times, first on the seventh plate, and the 

 outer branch twice more on the eighth and twentieth plate, and the 

 inner division at least once more about the twentieth plate, making 

 as many as ten arms to this ray. The left antero-lateral ray, after 

 its first division on the last brachial plate, gives off branches in 

 each division on the eighth plate, the outer division dividing twice 

 more on the eighth and twenty-second plate, and the inner division 

 once more on the twenty-second plate, which is as far as the arms 

 can be traced. There are at least ten arms each to these two rays, 

 and possibly more. The anterior ray is but partially exposed, and 

 seems to have an axillary plate about the twelfth series above the 

 last brachial. The first anal plate is nearly as large as the smallest 

 subradial, and rests between two of them, and a smaller second 

 anal rests upon the first, above which a double series of small 

 plates may be seen that probably form the base of a ventral tube. 

 Column rather stout, the first plates covering the whole diameter of 

 the truncated base. 



This species is closely related to Pot. concinnus, of Meek and 

 Worthen, Geol. Surv. of 111., Vol. 5, page 490, pi. 14, fig. 3, but 



